This invention relates broadly to a building construction, and more specifically to an automatically closing access door assembly for fire resistive floor/ceiling assembly of a building.
It is customary in modern buildings to make the floors of reinforced concrete or other material and to install the "utilities" in and below the floor. The utilities include, for example, plumbing, air ducts, communication, computer and electrical wiring. A ceiling or membrane is normally mounted below the utilities in order to separate the utilities from the space of the floor below.
In the past, "access doors" have also been provided in the ceiling which enable technicians to reach the utilities from the floor below, in order to service or modify them. Such an access door is described, for example, in U.S. Pat. No. 4,098,024 dated July 4, 1978. In the past, the primary requirement of the door design has been merely that it have an acceptable appearance and provide access to the space above.
It would be advantageous for such a door to also have fire or heat protection capability. Where the ceiling is made of a fire retardant material such as gypsum, it would be desirable to have the door capable of meeting at least the rating of the ceiling in order to maintain the fire rating of the floor/ceiling assembly. Such a door would be required to pass a fire test similar to the test required for a fire resistive floor/ceiling assembly. Fire protection capability is, of course, desirable in order to keep the fire from spreading to other locations and to protect the utilities from damage in the event of a fire in the floor space below.
Copending U.S. patent application Ser. No. 799,140, filed Nov. 18, 1985 discloses an access door which meets the fire ratings. The access door disclosed in U.S. Ser. No. 799,140 is designed to swing downwardly on a hinge to the open position, and in some instances a downwardly hanging door may interfere with the activities of the service technicians. The door also includes a return spring arrangement for closing the door.
It is therefore a general object of this invention to provide an improved ceiling access door assembly which has both an acceptable appearance and fire protection capability, and does not have a hinged door or a return spring.